1. Field of the Invention
The present invention relates to a portable exercise device and, more particularly, to a portable wrist exercise device used for strengthening the muscles of the hand, the wrist, and the forearm.
2. Description of the Prior Art
Devices specifically adapted to exercise the muscles of the hand, the wrist, and the forearm are known in the art. For example, the torsional wrist exerciser disclosed in U.S. Pat. No. 4,591,151 to Hensley includes a pair of handles which fit together in a sleeve-like arrangement and a torsion spring contained within the sleeve. The muscles of the hand, wrist, and forearm are exercised by rotating each of the handles against the resistance of the torsion spring. The spring wrist exerciser disclosed in U.S. Pat. No. 3,746,336 to Tanimoto includes a pair of grips grasped by each hand such that when the grips are turned about their longitudinal axis a pair of tension springs exert a resisting force of the rotation of the grips. U.S. Pat. No. 2,819,081 to Touraine discloses a rotating ring exerciser which includes a rotating ring positioned within a stationary ring and one or more set screws for locking the rings with respect to each other. The wrist muscles are exercised by turning the rotating ring against the frictional forces created by the set screws. In addition, a wrist exercise device comprising a pair of geared handles connected by an idler gear is known under the name SportsMate. The wrists are exercised by the forces created by a hand twisting one of the handles in direct opposition to an opposing force supplied by the other hand to the other handle.
Due to the public's increasing desire for physical fitness, the demand for new and improved exercise devices is growing. The known wrist exercise devices are not satisfactory for one reason or another. For example, the Hensley, Tanimoto and SportsMate devices all require that both hands be used simultaneously to operate the exercise device. The SportsMate device develops the resistance force from the user's hand on the opposite handle. Furthermore, the Touraine device employs frictional forces to resist the rotation of the ring member resulting in the weakening of the rotating ring and set screw after substantial use of the exercise device.
It is an object of the present invention to provide a wrist exercise device of a compact and lightweight structure that may be practiced with the use of only one hand or with the use of both hands. It is another object of the present invention to provide a wrist exercise device wherein the resistance force to the turning of one of the handles is not provided by the other handle and where the resistance force to the turning of either handle can be adjusted. A further object of the present invention is to provide a compact and lightweight wrist exercise device that can be used anywhere, that will exercise the muscles of the hand, wrist, and the forearm, and that is portable, durable, and easy to manufacture.